1. Field of the Invention
The present invention relates to a silicon wafer for a semiconductor substrate and the method for making the same and, more particularly, it relates to a silicon wafer for a semiconductor substrate having polycrystalline silicon deposited on the surface thereof and the method for making the same.
2. Description of the Prior Art
As shown in FIG. 1, in a conventional silicon wafer for a semiconductor substrate, only the front surface of a wafer body 1 is exposed and other surfaces are covered with a deposited polycrystalline silicon layer 2. Namely, in the conventional silicon wafer for a semiconductor substrate, the polycrystalline silicon layer 2 is provided on the side surfaces of the wafer body 1 besides the polycrystalline silicon layer 2 deposited on the back surface of the silicon wafer body 1, which is required for its function.
The above described conventional silicon wafer for a semiconductor substrate is manufactured by the following steps, namely, the polycrystalline silicon layer 2 is deposited on the entire surface of the wafer body 1 by chemical vapor deposition method and, thereafter, the mirror-like finishing is effected by the mechanochemical polish on the front surface of the wafer.
Meanwhile, U.S. Pat. No. 4,608,095 discloses reinforcing the getter effect by depositing a polycrystalline silicon of 0.05 to 2.0 .mu.m in thickness on the back surface of the semiconductor substrate. U.S. Pat. No. 4,053,335 discloses depositing polycrystalline silicon on the rear surface of the semiconductor substrate and sealing heavy metal movable ions in the polycrystalline silicon during high temperature processing.
In the above described conventional silicon wafer for a semiconductor substrate, the polycrystalline silicon 2 deposited on the periphery of the wafer body 1 is liable to peel off due to the abrupt change of the shape of the silicon wafer periphery during the manufacturing process of the semiconductor device. Therefore, in the silicon wafer for a semiconductor substrate obtained in accordance with the conventional manufacturing method, the polycrystalline silicon layer 2 on the periphery of the wafer body 1 is a cause of dust.